The full form of O₂ is oxygen gas, also known as dioxygen. This is the most common form of oxygen found in the Earth's atmosphere, comprising approximately 21%. Merriam-Webster defines oxygen as "a chemical element with atomic number 8 that constitutes 21 percent of the Earth's atmosphere". Oxygen is crucial for respiration in most living organisms and plays a vital role in numerous chemical processes. Testbook further emphasizes its importance, stating that "O2 is essential for respiration".
While O₂ represents the diatomic form, oxygen also exists in other forms, such as ozone (O₃). Britannica notes that oxygen exists in two allotropic forms: diatomic (O₂) and triatomic (O₃, ozone). Recent research has even discovered other forms, although O₂ remains the most prevalent and essential. Nature mentions a four-atom form of oxygen.
Oxygen's importance extends beyond respiration. It is a key component of water (H₂O) and various oxides found in the Earth's crust. Wikipedia highlights its abundance in the Earth's crust, present in various oxides such as water and carbon dioxide. Its dissolved form, dissolved oxygen (DO), is crucial for aquatic life and is a key indicator of water quality. EPA explains that "Oxygen is measured in its dissolved form as dissolved oxygen (DO)".
Key points about oxygen:
- Chemical Symbol: O
- Atomic Number: 8
- Common Forms: Diatomic oxygen (O₂), Ozone (O₃)
- Essential for: Respiration, various chemical processes, and life as we know it.
